[inlining] Add a clang option to control inlining of functions based on stack size

[wolfgangp]

Summary

Adding -finline-max-stacksize=<N> to clang. This generates the function attribute` inline-max-stacksize` (introduced in D129904, suppressing inlining of functions with stack sizes exceeding a specified limit.

[aeubanks]

perhaps a test that "inline-max-stacksze" doesn't appear if the flag isn't specified?

clang/docs/ClangCommandLineReference.rst

 .. option:: -finline-functions, -fno-inline-functions
 
 Inline suitable functions
 
 .. option:: -finline-hint-functions
 
 Inline functions which are (explicitly or implicitly) marked inline
 
+.. option:: -finline-max-stacksize=<arg>
+
+Suppress inlining of functions with a stacksize larger than <arg> bytes.
+
 .. option:: -fno-legacy-pass-manager, -fexperimental-new-pass-manager
 
 .. option:: -fno-sanitize-ignorelist, -fno-sanitize-blacklist
 
 Don't use ignorelist file for sanitizers
 
 .. option:: -fparse-all-comments
 

clang/include/clang/Basic/CodeGenOptions.def

 CODEGENOPT(EmitCodeView, 1, 0)
 
 /// Whether to emit the .debug$H section containing hashes of CodeView types.
 CODEGENOPT(CodeViewGHash, 1, 0)
 
 /// The kind of inlining to perform.
 ENUM_CODEGENOPT(Inlining, InliningMethod, 2, NormalInlining)
 
+/// The maximum stack size a function can have to be considered for inlining.
+VALUE_CODEGENOPT(InlineMaxStackSize, 32, UINT_MAX)
+
 // Vector functions library to use.
 ENUM_CODEGENOPT(VecLib, VectorLibrary, 3, NoLibrary)
 
 /// The default TLS model to use.
 ENUM_CODEGENOPT(DefaultTLSModel, TLSModel, 2, GeneralDynamicTLSModel)
 
 /// Bit size of immediate TLS offsets (0 == use the default).
 VALUE_CODEGENOPT(TLSSize, 8, 0)

clang/include/clang/Driver/Options.td

 def filelist : Separate<["-"], "filelist">, Flags<[LinkerInput]>,
                Group<Link_Group>;
 def : Flag<["-"], "findirect-virtual-calls">, Alias<fapple_kext>;
 def finline_functions : Flag<["-"], "finline-functions">, Group<f_clang_Group>, Flags<[CC1Option]>,
   HelpText<"Inline suitable functions">;
 def finline_hint_functions: Flag<["-"], "finline-hint-functions">, Group<f_clang_Group>, Flags<[CC1Option]>,
   HelpText<"Inline functions which are (explicitly or implicitly) marked inline">;
 def finline : Flag<["-"], "finline">, Group<clang_ignored_f_Group>;
+def finline_max_stacksize_EQ
+    : Joined<["-"], "finline-max-stacksize=">,
+      Group<f_Group>, Flags<[CoreOption, CC1Option]>,
+      HelpText<"Suppress inlining of functions whose stack size exceeds the given value">,
+      MarshallingInfoInt<CodeGenOpts<"InlineMaxStackSize">, "UINT_MAX">;
 defm jmc : BoolFOption<"jmc",
   CodeGenOpts<"JMCInstrument">, DefaultFalse,
   PosFlag<SetTrue, [CC1Option], "Enable just-my-code debugging">,
   NegFlag<SetFalse>>;
 def fglobal_isel : Flag<["-"], "fglobal-isel">, Group<f_clang_Group>,
   HelpText<"Enables the global instruction selector">;
 def fexperimental_isel : Flag<["-"], "fexperimental-isel">, Group<f_clang_Group>,
   Alias<fglobal_isel>;

clang/lib/CodeGen/CodeGenModule.cpp

void CodeGenModule::SetFunctionAttributes(GlobalDecl GD, llvm::Function *F,
   // jump table.
   if (!CodeGenOpts.SanitizeCfiCrossDso ||
       !CodeGenOpts.SanitizeCfiCanonicalJumpTables)
     CreateFunctionTypeMetadataForIcall(FD, F);
 
   if (getLangOpts().OpenMP && FD->hasAttr<OMPDeclareSimdDeclAttr>())
     getOpenMPRuntime().emitDeclareSimdFunction(FD, F);
 
+  if (CodeGenOpts.InlineMaxStackSize != UINT_MAX)
+    F->addFnAttr("inline-max-stacksize", llvm::utostr(CodeGenOpts.InlineMaxStackSize));
+
   if (const auto *CB = FD->getAttr<CallbackAttr>()) {
     // Annotate the callback behavior as metadata:
     //  - The callback callee (as argument number).
     //  - The callback payloads (as argument numbers).
     llvm::LLVMContext &Ctx = F->getContext();
     llvm::MDBuilder MDB(Ctx);
 
     // The payload indices are all but the first one in the encoding. The first

clang/lib/Driver/ToolChains/Clang.cpp

const Arg *InlineArg = Args.getLastArg(options::OPT_finline_functions,
                                          options::OPT_fno_inline_functions);
   if (Arg *A = Args.getLastArg(options::OPT_finline, options::OPT_fno_inline)) {
     if (A->getOption().matches(options::OPT_fno_inline))
       A->render(Args, CmdArgs);
   } else if (InlineArg) {
     InlineArg->render(Args, CmdArgs);
   }
 
+  Args.AddLastArg(CmdArgs, options::OPT_finline_max_stacksize_EQ);
+
   // FIXME: Find a better way to determine whether the language has modules
   // support by default, or just assume that all languages do.
   bool HaveModules =
       Std && (Std->containsValue("c++2a") || Std->containsValue("c++20") ||
               Std->containsValue("c++2b") || Std->containsValue("c++latest"));
   RenderModulesOptions(C, D, Args, Input, Output, CmdArgs, HaveModules);
 
   if (Args.hasFlag(options::OPT_fpch_validate_input_files_content,

clang/test/CodeGen/inline-stacksize.c

+// RUN: %clang_cc1 -O2 -emit-llvm %s -o - | FileCheck %s --check-prefixes NOOPT
+// RUN: %clang_cc1 -O2 -finline-max-stacksize=64 -emit-llvm %s -o - | FileCheck %s --check-prefix OPT
+
+void foo() {}
+
+// NOOPT-NOT: inline-max-stacksize
+// OPT:       define {{.*}}@foo{{.*}}#[[ATTR:[0-9]+]]
+// OPT:       attributes #[[ATTR]] = {{.*}}"inline-max-stacksize"="64"